Autoclave Temperature in Class N and Class B Autoclaves


Picture a life before sterilization. Imagine your dentist using the same devices he used in hundreds of others in your mouth. Or a doctor who performed surgery using devices that may have been boiled or soaked in alcohol. It’s no surprise so many people died in the early days from infection and illness. Thankfully, those days are over because of the autoclave. A device generating both high temperature and high pressure to sterilize equipment, laboratory materials and hazardous wastes; prior to reuse or disposal.

History of autoclaves

Charles Chamberland, in 1879, is credited to the invention of autoclave sterilizer. Researchers started to recognize the benefits of sterile surgery at that time; also doctors wanted a more effective form of sterilization than open flaming. The benefits of the autoclave quickly became apparent, and it became an integral part of every clinic and hospital.

What Is an Autoclave?

Autoclaves are somewhat similar pressure cookers to those you see in stores. If you’ve used pressure cookers, or are familiar with them, then you know that foods cook in a pressure cooker much faster than they do in a normal pot or oven. This is because of the constant heat and pressure that is exerted on the food. Against living micro-organisms the very same method works.

Micro-organisms are what many people also call germs. They are the bacteria, viruses, fungi, parasites, and so on that can cause our bodies to become infected. Spores are the micro-organisms immune to the environment. While they can endure harsher environments; they can still be killed if severe conditions are held for a prolonged period of time.

How an Autoclave works?

As done in an autoclave, the basic concept of steam sterilization is to expose every object to direct steam contact. It should be done at the appropriate temperature and pressure for the specified time. Therefore, steam sterilization has four parameters: steam, pressure, temperature, and time.

Steam and Pressure in Autoclaves

Dry saturated steam and entrained water are the ideal steam for sterilization (dryness fraction around 97 percent). Pressure acts as a means of getting the high temperatures required to destroy micro-organisms quickly. To ensure microbicidal activity precise temperatures must be achieved.

Autoclave Temperature

The two temperatures appropriate to steam sterilization are 121°C (250°F) and 132°C (270°F). Such temperatures (and other high temperatures) must be sustained to kill microorganisms for a limited period of time.

The explanation is that merely bringing something up to the boiling water temperature; 100 degrees Celsius (212 degrees Fahrenheit); isn’t enough to sterilize it since bacterial spores will withstand this temperature. By contrast, the sterilization is almost always sufficient at 121 degrees Celsius.

Exposures Times of Autoclaves

Recognized minimum exposure times of autoclaves are 30 minutes at 121°C; or 4 minutes at 132°C for the sterilization of wrapped healthcare supplies. Sterilization times at constant temperatures vary depending on the type of item (metal versus rubber, plastic, items with lumens); and whether the item is wrapped or unwrapped, and the type of sterilizer.

As a general rule, the higher the autoclave temperature, the shorter the process of sterilization. Many devices that do not need to be used can be stored overnight in the autoclave; while those that need to be reused immediately are subjected to higher temperatures for shorter time periods.

What industries use Autoclaves?

Autoclave use can be extended to different industries that involve sterilization of the equipment. Hygiene, disinfection, and sterilization are components that form part and parcel of various scientific occupations. The value of these components cannot be adequately emphasized. The numerous practitioners who would use autoclaves would include doctors, nurses, surgeons, beauticians and dentists.


Autoclave significance in the Medical Field

Hospitals, laboratories, and nursing homes couldn’t work without professional autoclaves; there is a continuous and critical need to sterilize instruments in such environments. Some instruments such as injectors, blades and forceps are designed for exclusive use whereas others are intended for reuse.

Autoclaves are the only way for such devices to ensure that people who work with the medical devices are not at risk of infection. Chances of re-use of equipment in third world countries are higher; making autoclaves very critical in providing safe treatment and care.

Before disposal, medical waste should also be sterilized to ensure that no one else gets contaminated after disposal. Autoclave is used as a means of sterilization in this situation. It’s become really common in application because it’s environmentally friendly.

Different Types of Autoclaves

Autoclave styles are diverse. Particularly in appearance, there is a simple autoclave which can be compared with a basic pressure cooker. It is a large pot that can be sealed onto the pot with a lid. This autoclave does the basic task of ensuring that the germs are destroyed by high temperature and pressure. This is often used in beauty parlors and school labs; but can also be used in science laboratories to a lesser degree.

There are bigger autoclaves in larger institutions such as hospitals. These autoclaves can cater to the demand and scale of the equipment being sterilized.

There is the positive pressure displacement autoclave and the negative displacement autoclave in terms of performance. Both operate with pressure but the negative autoclaves remove all the air from the chamber of the autoclave; while the positive one holds the air in, builds up enough steam and then displace it.

You can choose between two different classes when choosing an autoclave: Class N, and Class B.

Class N autoclave

Class N autoclaves are compact and are for basic materials to be sterilized. The letter “N” means “naked solid products”. Such autoclaves cannot therefore be used to sterilize textiles, porous loads, hollow objects or even items in pouches; as the processes do not have the necessary characteristics for passing different physical checks.

Another possible drawback of these machines is that class N autoclaves can’t guarantee the necessary steam penetration. It is contingent, among other things, on the initial formation of a vacuum, which is not necessary in these devices.

Class B autoclave

Class B autoclaves are compact but their level of efficiency is equivalent to that of hospital’s largest devices. The letter “B” means “big small sterilizers”, because they are small machines which give great efficiency. Every form of load in a Class B autoclave can be sterilized. This includes porous materials, pouch items, textiles, and hollow objects such as wands, turbines, and tips.

Please visit “Autoclave” section of our Lab Equipment products to browse through different types of autoclaves. We supply both Class N Autoclaves and Class B Autoclaves.

The Difference Between a Sterilizer and an Autoclave

Although many believe autoclaves are equivalent to sterilizers, they are more like parts of a tree. Sterilizers are the trunk from which autoclaves branch off. A sterilizer is a broad term for any device that can sterilize.

An autoclave sterilizer is a device specifically designed to sterilize equipment. The name is a mixture of two ancient words; auto- which is “self” in Greek, and clave- which is “key” is Latin. When the two terms are combined, it means “self-locking“.

This automatic lock feature is one of the things that sets the steam autoclaves apart from other sterilizers. Because an autoclave is a sterilizer, its function, like sterilizers, is to eliminate or remove all life forms on the surface of an object, such as bacteria, fungi, viruses, and spores.

While autoclaves only use steam to disinfect, sterilizers could use chemical substances, high pressure, filtration, irritation, or a combination of those methods to destroy living organisms.

Not all sterilizers can be autoclaves, since not every system can withstand the high temperatures needed to destroy any organism. If anyone were to use some form of equipment the material could melt and morph rendering it useless.


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